RE: [PATCH 1/2] Documentation: usb: dwc3: add power down clock scale property

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> -----Original Message-----
> From: Rob Herring <robh@xxxxxxxxxx>
> Sent: 2019年2月23日 8:33
> To: Jun Li <jun.li@xxxxxxx>
> Cc: mark.rutland@xxxxxxx; balbi@xxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; dl-linux-imx <linux-imx@xxxxxxx>
> Subject: Re: [PATCH 1/2] Documentation: usb: dwc3: add power down clock scale
> property
> 
> On Tue, Jan 22, 2019 at 10:37:17AM +0000, Jun Li wrote:
> > The USB3 suspend_clk input replaces pipe3_rx_pclk as a clock source to
> > a small part of the USB3 core that operates when the SS PHY is in its
> > lowest power(P3) state, and therefore does not provide a clock. The
> > power down scale specifies how many suspend_clk periods fit into a 16
> > KHz clock period, details can see DWC3 databook register
> > GCTL.PWRDNSCALE.
> >
> > Signed-off-by: Li Jun <jun.li@xxxxxxx>
> > ---
> >  Documentation/devicetree/bindings/usb/dwc3.txt | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt
> > b/Documentation/devicetree/bindings/usb/dwc3.txt
> > index 3e4c38b..d1c8b62 100644
> > --- a/Documentation/devicetree/bindings/usb/dwc3.txt
> > +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
> > @@ -102,6 +102,12 @@ Optional properties:
> >  			more than one value, which means undefined length INCR burst type
> >  			enabled. The values can be 1, 4, 8, 16, 32, 64, 128 and 256.
> >
> > + - snps,power-down-scale: Power down scale field specifies how many
> suspend_clk
> > +			periods fit into a 16 Khz clock period. When performing
> > +			the division, round up the remainder. Suspend clock is
> > +			from 32kHz to 125MHz, means the value range is 2~8000.
> > +			(details see DWC_usb3 databook register GCTL.PWRDNSCALE).
> > +
> 
> Sounds like the suspend_clk should be provided as a clock input so you can
> calculate this value.

Yes, I will go this approach by update dts with suspend_clk of dwc3

Thanks
Li Jun 
> 
> >   - in addition all properties from usb-xhci.txt from the current directory are
> >     supported as well
> >
> > --
> > 2.7.4
> >




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